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1974 Mazda Rx4 Resto-mod project

Old 01-02-16, 07:32 PM
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1974 Mazda Rx4 Resto-mod project

Hello, I just picked up a 1974 RX4.

It is currently a good drivers car but I am planning on some improvements.

I drove it around today. It's an interesting little beast and being the first time I have every driven a carbed car, it was weird having to pull a choke out to get it started. It's kind of a time warp sitting in the thing, old tech is kinda neat.

It looks like a good base to make a nice car out of. The body and chassis will be stripped and painted and the interior re-upholstered.


I do have a few qualms with it though.
1) it is under powered, but not as bad as I thought. It has an RX7 trans, and S4 RX7 13B with Hitachi 4Barrel carb.
2) The brakes are atrocious.
3) rear open diff
4) suspension is a little soft


If I can address all of these issues with simple bolt on parts then I may not need to do anything too drastic. I am taking advice and looking for resources on all four fronts.

Otherwise I will be taking the swap route and going turbo II or FD drivetrain. I have a complete wrecked FD so that is on my mind.

I was looking at the Camden Supercharger. Anyone have any experiences with a carbed 13B?



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Last edited by sip; 01-02-16 at 07:36 PM.
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Old 01-03-16, 08:45 AM
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The car looks great , no rust and fairly untouched . The fd format sounds like a good idea .I know the approach I take : less is more and when it comes to safety i do whats needed ( front brake upgrade ) . I always like to do upgrades that can be reversed if possible .I would leave the interior it looks great. good luck
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Old 01-03-16, 08:56 AM
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Very sweet looking car!!! I think it looks great just like it is!! like Matt said, do the needed upgrades to make it safe and enjoy that thing!! great find
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Old 01-06-16, 03:22 PM
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Very nice! Sorry I don't have input on your upgrades but she is beautiful.
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Old 02-29-16, 01:39 PM
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Great looking car! Really nice shape.
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Old 03-05-16, 10:29 AM
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Looks good sip, definitely worth bringing it cross country.
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Old 03-05-16, 05:31 PM
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The car is gorgeous, care to say what it cost you?
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Old 03-06-16, 10:37 PM
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Disassembled the whole car.






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Old 03-07-16, 10:33 AM
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While most of the car looks like this:



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There are some nooks where debris and moisture get trapped and cause rust:


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So I cut it out and will change the design to prevent rusting again and re-weld.


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Removing all the spot welds to clean underneath:


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Old 03-17-16, 07:56 PM
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I just picked up a set of metal fender flares:

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Old 03-18-16, 01:03 AM
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Did you get the fender flares yet? Are they just like the picture as in size? Iv been looking at buying a set also but the picture they show of just the flares look smaller.


Hey what's going on with that rear bumper on the white RX4 it has lights in it, never seen that before.


Keep up the good work...i need to get working on mine some day.

Last edited by SPENT-IT; 03-18-16 at 01:07 AM.
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Old 03-20-16, 07:57 PM
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Oh wow that thing looks great. I thought the RX-3's looked good with fender flares.
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Old 03-25-16, 12:27 AM
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That looked like a car I know from Victoria , BC . It was for sale at the 2015 All Japanese Meet I attended . The 1974 Coupe is the nicest RX-4 in my opinion (I have owned 3 of them).
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Old 03-26-16, 03:18 AM
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I'm falling in love with rx4's
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Old 03-26-16, 07:12 AM
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Looks like a great car! Mine had rust in the same spots, kind of a bad design from mazda. Also mice or chipmunks built nests inside mine so there was lots of debris to hold moisture and cause rot. As for the engine, I'm still debating going turbo fuel injected, or just keeping with what I have. Honestly, without serious modifications to the suspension and brakes the car really can't handle a lot of power. My half bridge 13B with twin weber 36dcd carbs makes more than enough power to make the car feel scary.
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Old 03-27-16, 09:42 AM
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Originally Posted by Narfle View Post
I'm falling in love with rx4's
Funny you say that...I just fell in love with mine again after a breif 6 month restoration.

To the OP. Great starting platform, looking forward to the process and the final product
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Old 03-27-16, 06:24 PM
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Originally Posted by SPENT-IT View Post
Did you get the fender flares yet? Are they just like the picture as in size? Iv been looking at buying a set also but the picture they show of just the flares look smaller.


Hey what's going on with that rear bumper on the white RX4 it has lights in it, never seen that before.


Keep up the good work...i need to get working on mine some day.

I won't have them for a few weeks, I'll let you know. Front should be 3 in from body rear should be 4 inch.

Originally Posted by Redline-RX3 View Post
That looked like a car I know from Victoria , BC . It was for sale at the 2015 All Japanese Meet I attended . The 1974 Coupe is the nicest RX-4 in my opinion (I have owned 3 of them).
This is she, I had her shipped across country.


Originally Posted by Narfle View Post
I'm falling in love with rx4's

I did also.

Originally Posted by Buggy View Post
Looks like a great car! Mine had rust in the same spots, kind of a bad design from mazda. Also mice or chipmunks built nests inside mine so there was lots of debris to hold moisture and cause rot. As for the engine, I'm still debating going turbo fuel injected, or just keeping with what I have. Honestly, without serious modifications to the suspension and brakes the car really can't handle a lot of power. My half bridge 13B with twin weber 36dcd carbs makes more than enough power to make the car feel scary.
Really how much power/tq does that set-up make?

Originally Posted by papsmagu View Post
Funny you say that...I just fell in love with mine again after a breif 6 month restoration.

To the OP. Great starting platform, looking forward to the process and the final product
Thanks. I have only driven the car around the block twice. I did like it, but thought there were some improvements to be made.
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Old 03-28-16, 09:17 PM
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Really how much power/tq does that set-up make?
I'm not sure as I've never had time yet to put it on the dyno. I want to get that done this spring and fine tune it. I'm guessing close to 200whp. It dynoed at 156whp at 7,000 rpm when I first built it years ago with stock coils and a 48 IDF weber on it. At 7k it was still making power too, just too much load on the dyno and the run was too long it was starting to get hot. It pulls strong now to 9,000 rpm.
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Old 03-29-16, 07:38 AM
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I drove mine for about 6 months after i bought it. It had all original suspension, bushings and tie rod ends. One of the things that i did, was replace the front suspension to coilovers, replaced all bushings, tie rod ends and any other suspension part that could be replaced along with disk brakes. Took it out this weekend and it really drove like a different car. It handles great at high speeds. I can only imagine what yours will be like when its done. Keep up the good work and keep us posted on your progress. Any thoughts on paint color, wheels and engine?
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Old 03-29-16, 06:27 PM
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Originally Posted by papsmagu View Post
I drove mine for about 6 months after i bought it. It had all original suspension, bushings and tie rod ends. One of the things that i did, was replace the front suspension to coilovers, replaced all bushings, tie rod ends and any other suspension part that could be replaced along with disk brakes. Took it out this weekend and it really drove like a different car. It handles great at high speeds. I can only imagine what yours will be like when its done. Keep up the good work and keep us posted on your progress. Any thoughts on paint color, wheels and engine?


Here are some colour choices I have been interested in. The Interior is going to be full brown leather with back door panels and dash.

I have some candidates, they are all quite different in different lighting conditions.


Cement Grey:





Porsche Fashion Grey:





Audi Nardo Grey:



Toyota Quicksand:






I am open to suggestions, however not looking for something crazy Orange or Yellow.







Wheels I'm thinking Work CR01, also looking for others in 16x9ish near 0 offset



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Old 03-30-16, 08:41 AM
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i like the Toyota Quicksand ...and the wheels are SICK! i would go with the Matte Gunmetal with the Bronze lips....i think they would look awesome with the brown leather interior. i was able to squeeze a 16x9.5 ET -6 in the back of mine. sticks out a bit but that is the look i was going for. Work has some good size options.
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Old 03-30-16, 10:40 PM
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^ I have been thinking about an NA 20B for the car. I found your REPU 20B and wanted to know how that worked out. the length of the engine and how you mounted it (is it just on the front cover like the original 13B?) is it farther forward or farther back the the 13B? did you have any interferences with the steering box and knuckles?
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Old 03-31-16, 09:07 AM
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Originally Posted by sip View Post
^ I have been thinking about an NA 20B for the car. I found your REPU 20B and wanted to know how that worked out. the length of the engine and how you mounted it (is it just on the front cover like the original 13B?) is it farther forward or farther back the the 13B? did you have any interferences with the steering box and knuckles?
Ohhhhh i would be so jealous....i always wanted my rx4 to have a 4 rotor.....its just fitting isn't it??? a three rotor would also be just as cool. You can fit a three rotor in the rx4 engine bay with no problem. there is plenty of room.

my repu has the the 1st gen front cover so that engine mounts are up front. I could not install the stock engine mounts as they were in conflict with my drag link. I love to drive the repu. super reliable and great fun to drive. I 20B sits about 6" further forward than the stock 13B. I had to modify the tranny. the tranny made up 4" of the 6" so the shifter location ended up being 2" further back than the stock location. Again, its no big deal and everything looks stock.


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Old 03-31-16, 04:02 PM
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This car is gonna be nuts! I remember seeing this one for sale and being so tempted to pick it up. The only issue was that it was in Canada and I had not bought a Canadian car before.
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Old 04-01-16, 10:09 AM
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Originally Posted by papsmagu View Post
Ohhhhh i would be so jealous....i always wanted my rx4 to have a 4 rotor.....its just fitting isn't it??? a three rotor would also be just as cool. You can fit a three rotor in the rx4 engine bay with no problem. there is plenty of room.

my repu has the the 1st gen front cover so that engine mounts are up front. I could not install the stock engine mounts as they were in conflict with my drag link. I love to drive the repu. super reliable and great fun to drive. I 20B sits about 6" further forward than the stock 13B. I had to modify the tranny. the tranny made up 4" of the 6" so the shifter location ended up being 2" further back than the stock location. Again, its no big deal and everything looks stock.






Do you have any photos of the engine swap progress, mounts etc?The photos in your thread have broken links.
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